Vast systems of ancient caverns on Mars may have captured enormous floodwaters

Dec 04, 2012

(Phys.org)—An international research team led by the Planetary Science Institute has found evidence that indicates that approximately 2 billion years ago enormous volumes of catastrophic flood discharges may have been captured by extensive systems of caverns on Mars, said PSI research scientist J. Alexis Palmero Rodriguez.

Rodriguez and the research team came to this conclusion after studying the terminal regions of the Hebrus Valles, an outflow channel that extends approximately 250 kilometers downstream from two zones of surface collapse.

The Martian outflow channels comprise some of the largest known channels in the solar system. Although it has been proposed their discharge history may have once led to the formation of oceans, the ultimate fate and nature of the fluid discharges has remained a mystery for more than 40 years, and their excavation has been attributed to surface erosion by glaciers, debris flows, catastrophic floodwaters, and perhaps even lava flows, Rodriguez said.

The PSI-led team's work documents the geomorphology of Hebrus Valles, a Martian terrain that is unique in that it preserves pristine landforms located at the terminal reaches of a Martian outflow channel. These generally appear highly resurfaced, or buried, at other locations in the planet. Rodriguez and his co-authors propose in an article titled "Infiltration of Martian overflow channel floodwaters into lowland cavernous systems" published in Geophysical Research Letters that large volumes of catastrophic floodwaters, which participated in the excavation of Hebrus Valles, may have encountered their ultimate fate in vast cavernous systems.

They hypothesize that evacuated subsurface space during mud volcanism was an important process in cavern development. Mud volcanism can expel vast volumes of subsurface volatiles and sediments to the surface. But because evacuation of subsurface materials generally occurs within unconsolidated sediments resulting caverns are transient and mechanically highly unstable.

However, the investigated Martian caverns appear to have developed within permafrost, which at -65 degrees Celsius (-85 degrees Fahrenheit)—a typical mean annual surface temperature for the investigated latitudes—has a mechanical strength similar to that of limestone. Limestone rocks host most of the terrestrial cavern systems.

Possible caverns have been recently identified on Mars, and their existence has caught much scientific and public attention because of their potential as exobiological habitats. However, their age and dimensions remain uncertain. The discovery of vast caverns that existed in ancient periods of Mars shows that these habitats may have in fact existed during billions of years of the planet's history, Rodriguez said.

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It should be frozen, if it is there at all. This area isn't close enough to the equator for it to melt.

There are lava tubes near the surface in other areas, closer to the equator though. The problem, of course, is that you really probably want to check several different lava tubes, and they are probably too far apart to check two of them with one mission.

A rover designed to be more mobile and cover more land might eventually be desirable, especially if a particular site is under considderation for a human landing. If you knew that you'd be able to investigate things in detail later, it would be nice to do a survey of all the things around. Maybe you could even set up something like Google Maps Street View?

GSwift7: I agree that the water should be frozen. If you pour water into a cavern carved from permafrost, it just seems likely that the water will freeze, especially at -65C. I doubt that there would be enough water, at a high enough temperature, to melt all of the permafrost, and even if it did, at Mars' temperatures, it would refreeze.

Related: NASA wants to send a duplicate of Curiosity to Mars. Maybe it could be reconfigured to investigate at least one lava tube?

Related: NASA wants to send a duplicate of Curiosity to Mars. Maybe it could be reconfigured to investigate at least one lava tube?

I'm sure that ranks really high on the list of possible targets. The problem with lava tubes is that the ones we have identified from satellite images are visible only because they have what are called skylight features, where they have partially collapsed. It might be risky driving a 2000 lb rover near such a feature. The ground near the skylight could be weak. I think you would want some kind of extendable boom, so that you could keep your distance and then lower your instruments into the hole on a cable. That's an awefull lot of mass and engineering work for such a specific target. Then there's not any garuantee that there's anything interesting inside the tubes either.

True, if all we have are "skylights". I was thinking of the lava caves I've been in, with horizontal entrances. In that case, all we'd need would be a detachable communications unit and a long cord on a reel. Oh well...maybe someday.

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